Electrical protective devices



Jan. 10, 1967 G FRADLEY ETAL 3,297,839

ELECTRICAL PROTECTIVE DEVICES Filed Feb. 10, 1966 3 Sheets-Sheet 1 APPLICANTS FIG.1

Gordon Albert Fradley 8c Malcolm whi 0 me Jan. 10, 1967 FRADLEY ET AL 3,297,839

ELECTRICAL PROTECTIVE DEVICES 3 Sheets-Sheet 2 Filed Feb. 10, 1966 3 mb K I mw wm .H i K 3 ,5 9 9 1 -ENmQM N BE .3 mm 3 m9 3 09 Q 09 Q i: m? mm PR9 a \N: 1 F J I I E a 0o 3 1 c Jan. 10, 1967 FRADLEY ETAL 3,297,839

ELECTRICAL PROTECTIVE DEVICES Filed Feb, 10, 1966 3 Sheets-Sheet 5 United States 3,297,839 ELECTRICAL PRGTECTIVE DEVECES Gordon Albert Fradley and Malcolm Whitehouse, Stafford, England, assignors to The English Electric Company Limited, London, England, a British company Filed Feb. 10, 1966, Ser. No. 526,429 Claims priority, application Great Britain, Feb. 10, 1965, 5,788/ 65 9 Claims. (Cl. ZOO-50) This invention relates to electrical apparatus com prising a movable cradle mounted within a casing, the

cradle being adapted to support, for example, an electrical relay or other electrical instrument.

According to one aspect, the invention consists in electrical apparatus comprising a movable cradle mounted within a casing, and locking means selectively operable to lock and unlock the cradle, the locking means including a catch and co-operating latch which is movable in one direction from a normal position of rest to unlock the cradle and permit withdrawal thereof from a predetermined location in the casing, the locking means being so disposed that the catch is arranged to engage the latch upon the cradle advancing towards the said location and move the latch in said one direction whereby, upon the cradle returning to the said location, the latch is permitted to assume its rest position and lock the cradle within the casing, and a device carried by the latch which engages a link operable directly upon a switch and is effective to displace the link in one direction, to open the switch, and in the opposite direction, to close the switch, in response to movement of the latch away from and towards its rest position, respectively.

The latch and the catch may be so shaped that the latch must be initially displaced from its rest position to permit the catch to move the latch in said one direction upon the cradle advancing towards the said location.

Furthermore, the cradle may carry a plurality of first contacts for engaging with cooperating second contacts mounted in said casing, the arrangement being such that the said switch is opened before the first and second contacts disengage upon the withdrawal of the cradle and is made only after the first and second contacts have engaged upon the advance of the cradle into said casing.

In order that the invention can be fully understood, one embodiment thereof will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view from the front of a protective relay case, the cover being removed to reveal the internal construction;

FIG. 2 is a longitudinal section of the assembled relay case;

FIG. 3 is a part-sectional view of the front part of the relay with its cradle in an intermediate position;

FIG. 4 is a simplified sectional view of part of the relay with its cradle in a further intermediate position.

Referring now to FIGS. 1 and 2 the relay comprises a case 11, a slidable cradle 12 and a cover 13.

The case 11 has a shell of sheet steel material which is formed with a top 14, a back 15, and two opposing sides 16. Attached to the sides by screws 17 is a moulded member 20 of insulating material which forms the bottom of the relay, and the cover 13 is carried by a flange 21 on the front of the relay.

The flange 21 has three of its sides formed integrally with the top 14 and sides 16 and has its fourth side provided by an L-shaped steel member 22 formed with a lip 23. The lip 23 extends horizontally over part of the moulded member 20 thereby to provide location and ice protection for the moulded member. Headed studs 24, held captive by circli-ps 25, are provided on this flange 21 at the base of the relay.

A locking catch 32: is attached, e.g. by rivets 33, to each side 16 o'f'the case, as also is a pressure spring 34 and a locating pin 36.

The moulded member 20 has mounted on it ten spaced contact members 42 which are secured in position by screws 43 and 44 and these latter screws engage bent-up portions of each contact member and cooperate with inserts 45 moulded into the rear flange of the moulded member 20. In order to provide a robust mounting for the inserts 45, protruding bushes 46 are provided on the back of this flange, and each insert 45 forms with its corresponding bush 46 a terminal connection 47 from which a lead (not shown) can be taken to apparatus external of the relay.

In order to allow sufiicient room for the terminal connections 47 at the back of the relay they are staggered in two rows of five, and in FIG. 2 it will be seen that to enable the connections therewith to be made internally, alternate contact members are bent downwardly, as shown at 48.

The cradle 12 of the relay has a chassis formed with two U-shaped members 54 and 55 riveted at 56 and 57 respectively to two similar upright members 58.

Carried between the two arms of the U-shaped member 54 at the bottom of the chassis is a moulded movingcontact insulating support member 59 which is attached to the member 54 by screws (not shown) which cooperate with pin members 61 set into flanges 62 formed in the support member. On its underside, the support member 59 carries a contact member 63 and nine other contact members, one of which is shown at 64. The contact members 63 and 64 are arranged parallel to one another and are separated by lands 65 formed in the support member.

The contact members 63 and 64 are similar in that they are each provided with two springs 67 to provide spring loading for the contact members and also to provide positive location for the cradle in the case as will be explained more fully later. In addition, each contact member is provided at its free end with a lip 68 for engaging the bottom of a recess 69 formed in the support member 59 thereby to limit movement of each contact member under the action of its associated springs 67 when the cradle is removed from the case.

The contact members 63 and 64, however, differ in length and in this respect will be described separately, the single contact member 63 being described with reference to FIG. 2 and one of the nine contact members 64 being described with reference to FIG. 3.

The contact member 63 through which the section of FIG. 2 is taken is the third contact member from one side 16 as can be seen in FIG. 1.

Referring now to FIG. 2 it will be seen that the contact member 63 is secured to the support member 59 by screw '70. This screw extends through the support member and is provided with a nut 71 to hold in position, and make electrical contact with a spring contact piece 72. The contact piece 72 is further secured to the support member by a screw 73 and carries at its free end a contact tip 74.

Also attached to the support member is a further spring contact piece 75 which carries a contact tip 76 at its free end and is attached to the support member 59 by a screw 77. The other end of the contact piece 75 is bent round the back edge 80 of the support member to the underside thereof where it provides a contact surface 81. i

It will be seen that the contact pieces 72 and 75 together form a means by which an electrical connection between the contact member 63 and the contact surface 81 may be made or interrupted by appropriate movement of the contact tips 74 and 76, and this combination .together with further means later to be described, will hereafter be called an isolating switch 82.

It should be understood that although in FIG. 3 the isolating switch 82 is shown, it is not directly associated with any of the contact members 64.

Referring now to FIG. 3, which shows a section taken through the contact 64 (FIG. 1), it will be seen that each contact member 64 has one end 83 at the back edge 80 of the support member 59 and is secured in position by a screw 84.

Between its respective screw 77 or 84 and the back edge 80 of the support member 59, the further contact piece 75 and each contact member 64 are each formed with a hole through which passes a further screw 85 to engage a hexagonal insert 86 in a corresponding recess in the support member.

Each further screw 85 secures in position an electrical connection shown in part at 87 which thus makes electrical contact with its associated contact member 64 or contact surface 81 and is further connected to electrical apparatus, e.g. a relay, carried by the cradle. This apparatus is not relevant to the invention itself and is therefore only denoted in outline at 90 in FIG. 2.

Support for the electrical apparatus is provided by the two U-shaped members 54 and 55, the top member 55 of which also serves to support four rollers 91 on rivets 92. Each roller 91 is rotatably mounted on its associated rivet to project above the top edge of the member. r

Carried on the outside of the upright member 58 is a locking latch 93 which is rotatably supported by a pin 94, this pin passing through the upright member and having a head 95.

On the other side of the head 95 there is formed a further pin 96 which is eccentric with the pin 94 and is slidable betwen two arms 97 provided at one end of an L-shaped isolating-switch operating member 98. This latter member is provided with two slotted holes 100 for engagement with the pin members 61.

At its other end, the operating member 98 is bent inwardly of the cradle and has attached to it by a screw 102 an insulating member 103, and the operating member 98 and the insulating member 103 together with the contact piece 72 and the further contact piece 75 form the isolating switch 82 previously mentioned.

The latch 93, which carries the pin 96 for operating the isolating switch 82, is formed with a heel part 104, a toe part 105, and a fiat edge 106, and this latch is, in addition, bent inwardly at 107 to form a lug as shown.

The latch on the other side of the relay is shown at 108 in FIG. 1; it differs from the latch 93 only in that its supporting pin 94 is plain, having no further pin 96 formed on its head 95. No isolating switch is provided for the latch 108.

The cover 13 (FIG. 2) has a frame 110 of moulded material having a window into which glass 111 is held by spring washers 112 and pins 113. Secured to and extending along part of the top of the frame is a U-section steel clip member 114 and at the two bottom corners of the frame 110 are provided captive hand nuts 116.

A spring-loaded relay-flag resetting device is generally shown at 120, and this has a resetting member 121.

The relay is shown in FIG. 2 to be in its operating position with the cradle fully to the back of the case and ,the cover in position.

91 which are pressed against the top 14 of the case by the springs associated with the contact members of the cradle. Location between the sides 16 of the case is provided by the pressure springs 34 carried on the case which cooperate with the arms of the U-shaped member 54.

It will be noted in FIG. 2 that the cover 13, when in position, almost abuts the lugs 107 and thereby prevents the latches from moving substantially from their closed position if the relay is subjected to vibration and shock.

To withdraw the cradle such as might be necessary, for instance, for checking or resetting contact clearances in the electrical apparatus 90, the cover 13 is first removed by unscrewing the hand nuts 116 from the studs 24 and unclipping the cover from the flanges 21.

Removal of the cover allows the latches 93 and 108 to be rotated in an anticlockwise direction as shown in the drawings and by so doing the isolating switch 82 is opened and the locking catches 32 disengaged.

The cradle can then be withdrawn completely from the case.

It will be noted that as the cradle is removed it is guided initially by all four rollers 91. After the front two rollers 91 have left the case and the contact members carried by the case and the cradle are no longer in contact, guidance is by the back pair of rollers 91 and the locating pins 36 acting on the underside of the U-shaped member 55.

To push the cradle back into the case and lockit into position the procedure is essentially reversed.

The latches 93 and 108 are first turned to their open position and the cradle then placed into a position for entry into the case by resting the underside of the end of the U-shaped member on the locating pins 36. The cradle is then pushed fully into the case until the backs of the U-shaped members 54 and 55 prevent further movement by abutment against the back of the case. The latches can then be turned in a clockwise direction as shown in the drawings to lock the cradle in the case by engagement with the locking catches 32 and to close the isolating switch 82 by horizontal movement of the L- shaped member 98.

If it should happen that, when the cradle is entered into the case, one or both of the latches are in an intermediate position relative to the cradle similar to that shown in FIG. 3, then movement of the cradle into its closed position causes a latch 93 or 108 which is in an intermediate position to turn to its fully open position by cam action of the locking catches 32 on the part of the latch which lies between its heel 104 and its toe 105, such cam action being as shown in FIG. 3.

By arranging that the opening of the latch 93 by such cam action causes its isolating switch 82 to open before the associated contact members of the case and the cradle come into contact with one another, it is thereby ensured that the circuit associated with the isolating switch can only be made when the cradle is in its fully closed position and inadvertent operation of apparatus external of the relay and connected into the circuit is therefore avoided.

If an attempt should be made to enter the cradle into the case with one or both of the latches completely in their closed or rest position, or almost so, then movement of the cradle is prevented by abutment of the heel 104 of each closed latch against the front end of the corresponding locking catch, as shown in FIG. 4. In this position further clockwise rotation of the latch is prevented by its flat edge 106 which is obstructed by the corresponding end of the U-shaped member 55. To close the cradle, each closed latch must first be opened, or partially so, and the cradle can then be pushed fully home and locked into position.

It will thus be seen that by providing the catches 32 not only are means provided for locking the cradle into its closed position but also for ensuring that electrical apparatus externally of the relay and connected into the circuit with which the isolating switch is associated cannot be operated inadvertently during movement of the cradle.

In addition it is also rendered unnecessary to open the latches any further if they are in an intermmediate posi* tion when the cradle is to be closed.

The embodiment shown includes positive catches which are carried by the case and arranged to cooperate with slotted latches carried by the cradle. Alternatively, however, the male members could be carried by the latches and the female members carried by the case. Alternatively, the latches may themselves be carried by the case and arranged to cooperate with catches on the cradle.

Although the latches were shown to engage the catches and effect rotational movement, if desired, they may engage the catches and effect linear movement, and they may act indirectly through one or more additional members.

Furthermore, the rollers are shown to be carried by the cradle to abut against the case during closure of the cradle and when the cradle is in its closed position. However, the rollers may alternatively be carried on the case and be biased against members which comprise part of the cradle.

Biasing for the rollers is preferably provided by springs provided for relatively slidable contact members as shown, but alternatively or additionally it may be provided in the mountings of the rollers themselves or by leaf springs such as for example might be attached to a bottom U- shaped member, e.g. 54, to cooperate with the top of flanges 27 on a moulded member 20.

What we claim as our invention and desire to Letters Patent is:

1. Electrical apparatus comprising,

a casing,

a cradle mounted for movement within the casing,

locking means selectively operable to lock and unlock the cradle, the locking means including a catch and a latch cooperating therewith, the latch being movable in one direction from a normal position of rest to unlock the cradle and permit withdrawal thereof from a predetermined location in the casing,

mounting means for mounting the locking means in a manner such that said catch is arranged to engage said latch upon the cradle advancing towards said location and move said latch in said one direction whereby, upon said cradle returning to said location, said latch is permitted to assume its rest position and lock the cradle within the casing,

an actuating device secured to said latch,

a link mounted for movement on said cradle and in direct engagement with said actuating device, and

a switch engagable by said link, said actuating device secure by being efiective to displace the link in one direction, to open the switch, and in the opposite direction, to close the switch, in response to movement of said latch away from and towards its said rest position, respectively.

2. Apparatus according to claim 1, wherein said latch is mounted on said cradle and said catch is mounted on said casing.

3. Apparatus according to claim 2, wherein the said latch is rotatably movable about an axis.

4. Apparatus according to claim 3, wherein said latch comprises a plate, said plate including means defining an arcuate slot substantially coaxial with said axis, said catch being arcuate in form for engagement with the slot to lock the cradle.

5. Apparatus according to claim 4, wherein said actuating device comprises a pin which is displaced from said axis, and said link includes means defining a rectilinear slot with which said pin engages.

6. Apparatus according to claim 5, wherein said link is L-shaped, one arm of the link including said means defining the rectilinear slot and the other arm being eflective to open and close said switch.

7. Apparatus according to claim 4, wherein said catch includes an end portion so shaped in relation to said latch as to abut the latch in its said rest position upon the cradle advancing towards said location, whereby said latch must be initially displaced from said rest position to permit the catch to move the latch upon the cradle advancing towards said location.

8. Apparatus according to claim 2, wherein said cradle comprises a plurality of first contacts, and said casing comprises a plurality of second contacts for engaging with said first contacts, said switch being opened before the first and second contacts disengage upon withdrawal of the cradle and said switch being closed only after the first and second contacts have engaged upon the advance of the cradle into said casing.

9. Apparatus according to claim 8, comprising a relay supported on said cradle, and means connecting said switch to a trip circuit so that, at break, said trip circuit is isolated.

No references cited.

ROBERT K. SCHAEFER, Primary Examiner. R. J. SCOTT, Assistant Examiner. 

1. ELECTRICAL APPARATUS COMPRISING, A CASING, A CRADLE MOUNTED FOR MOVEMENT WITHIN THE CASING, LOCKING MEANS SELECTIVELY OPERABLE TO LOCK AND UNLOCK THE CRADLE, THE LOCKING MEANS INCLUDING A CATCH AND A LATCH COOPERATING THEREWITH, THE LATCH BEING MOVABLE IN ONE DIRECTION FROM A NORMAL POSITION OF REST TO UNLOCK THE CRADLE AND PERMIT WITHDRAWAL THEREOF FROM A PREDETERMINED LOCATION IN THE CASING, MOUNTING MEANS FOR MOUNTING THE LOCKING MEANS IN A MANNER SUCH THAT SAID CATCH IS ARRANGED TO ENGAGE SAID LATCH UPON THE CRADLE ADVANCING TOWARDS SAID LOCATION AND MOVE SAID LATCH IN SAID ONE DIRECTION WHEREBY, UPON SAID CRADLE RETURNING TO SAID LOCATION, SAID LATCH IS PERMITTED TO ASSUME ITS REST POSITION AND LOCK THE CRADLE WITHIN THE CASING AN ACTUATING DEVICE SECURED TO SAID LATCH, A LINK MOUNTED FOR MOVEMENT ON SAID CRADLE AND IN DIRECT ENGAGEMENT WITH SAID ACTUATING DEVICE, AND A SWITCH ENGAGEABLE BY SAID LINK, SAID ACTUATING DEVICE BEING EFFECTIVE TO DISPLACE THE LINK IN ONE DIRECTION, 